1. Field of the Invention
The present invention relates generally to magnetic tape read and/or write heads, and more particularly to magnetic tape read and/or write heads having mini-outriggers adjacent active data islands.
2. Description of the Related Art
Magnetic tape continues to be an efficient and effective medium for data storage in computer systems. Increased data storage capacity and retrieval performance is desired of all commercially viable mass storage devices and media. In the case of linear tape recording, a popular trend is toward multi head, multi-channel fixed head structures with narrowed recording gaps and data track widths so that many linear data tracks may be achieved on a tape medium of a predetermined width, such as one-half inch width tape. To increase the storage density and reduce access time of magnetic tapes, data tracks on the tape are arranged with greater density and the tape is streamed by a tape head at increasingly faster rates.
Magnetic tape heads typically include an active device region with embedded transducers across which the magnetic tape advances. The data transducers are included on raised strips or ridges, commonly referred to as data islands or bumps, which provide a raised tape support or wear surface for which the magnetic tape wraps around during use. In other examples where the tape is flown over the head structure, data transducers may be included on a contoured head surface having aerodynamic bleed slots or the like, which cause the tape separation to be reduced over the data transducers.
FIG. 7 illustrates an exemplary multi-bump head 720 having three data islands 724 and two outriggers 726. Data islands 724 include one or more data transducers. The data transducers may include recording elements for writing information onto a magnetic tape and/or reproducing elements for reading information from a magnetic tape. An embedded recording element produces a magnetic field in the vicinity of a small gap in the core of the element, which causes information to be stored on magnetic tape as it moves across the support surface. In contrast, a reproducing element detects a magnetic field from the surface of magnetic tape as the tape moves over the support surface. Typically, the center island 724 will include write elements and the outer islands 724 include read elements to perform read-write functions in both directions as is known in the art. Modem heads generally utilize photolithography and MR head technology, able to deposit a combination read and write elements on the same island, where typically only two bumps are needed for forward and reverse operation.
Additionally, conventional heads may be provided with “outrigger” islands on both sides of the head which help support the tape and control the wrap angle of the tape with the island therebetween. Outriggers, e.g., outriggers 726, are generally similar in size and shape to islands 724. Exemplary head configurations, including data islands and outriggers, are described in U.S. Pat. No. 4,809,110, which is hereby incorporated by reference in its entirety as if fully set forth herein.
Generally, there is a microscopic separation between an active device region of the tape head, including recording and reproducing elements, and the tape during operation that reduces the strength of the magnetic field coupled to the tape surface during the recording process. The small separation reduces the coupling between the tape field and the reproducing element, causing a signal loss. This reduction in magnetic field strength is generally referred to as a “spacing loss.” The magnetic field strength detected by a tape or a reproducing element is proportional to e−kd/λ, where d is the head-to-tape separation, λ is the recording wavelength, and k is a constant. The detected magnetic field strength decreases exponentially both with respect to separation between the tape and the support surface and with respect to recording density (which is inversely related to the recording wavelength). Thus, while a limited amount of head-to-tape separation might be acceptable at low recording densities (100-200 KFCI), smaller transducers used with magnetic tapes of higher recording densities (over 200 KFCI) can tolerate little to no head-to-tape separation.
Further, to allow for faster access and write times, the media may be advanced by a head at speeds ranging from 100 to 1,000 inches per second or more. Increased media speed, however, may entrap air between a support surface of the head and media. Improper contour at one extreme may allow the air to cause separation or at the other extreme it could result in excessive high contact pressure between the media and the support surface leading to signal loss and/or excessive damage to the media.
The amount of head-to-tape separation may be reduced by adjusting the wrap angle of the tape around the head structures (e.g., the outriggers and the islands) to create tension in the tape and reduce the amount of air that may become entrapped. However, increased tension may cause an increase in the contact pressure between the tape and head that may damage the media and/or the head. One method to reduce pressure includes reducing the wrap angle according to the principles described in U.S. Pat. No. 4,809,110, entitled NARROW CONTOUR HEAD ASSEMBLY. The '110 patent describes, for example, that if the wrap angle is too large, a bubble or arc may occur, creating a separation between the tape and the head structure. Further, if the wrap angle is too small the tape may entrap air as it advances over the head structure and increases the separation therebetween. Accordingly, high-speed tape drive systems are generally designed with precise tape paths and contoured tape heads to achieve a desired wrap angle. Manufacturing contoured tape heads with desired wrap angles is generally costly and complicated.
Increased tension in the tape and resulting pressure between the storage media and the head to prevent spacing loss has several deleterious consequences to both the storage media and the head. For example, increased tension and pressure may reduce tape life and increase the possibility of tape damage and data loss. Tape damage may lead to increased lateral tape motion and decreased reliability. Increased tension and pressure may also cause the head structure and tape to wear more quickly resulting in shortened tape and head life.
What is desired is a read/write head structure that presents an appropriate wrap angle to the magnetic tape to decrease spacing loss between the active device regions and the magnetic tape and reduce pressure (and resulting wear) between the magnetic tape and the head structure. Further, a head structure with reduced manufacturing complexity and cost is desired.